Verifying availability of idle-mode mobile subscriber station in wireless access system

ABSTRACT

A method of verifying availability of a mobile subscriber station that is in an idle-mode includes requesting to a base station by the mobile subscriber station to enter an idle-mode, wherein the base station is associated with a paging group comprising a plurality of base stations, and receiving from the base station an idle-mode response command to enter the idle-mode. The method also includes receiving from the base station a paging command comprising an action code associated with performing ranging while the mobile subscriber station is in the idle-mode to verify availability of the mobile subscriber station with respect to the base station, wherein if the ranging is not successfully performed with the base station during a predetermined period, the base station continues to transmit the paging command until a paging retrial count reaches a predetermined threshold.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.11/691,410, filed Mar. 26, 2007, now U.S. Pat. No. 7,505,776, which is acontinuation of U.S. application Ser. No. 11/165,744, filed Jun. 24,2005, now U.S. Pat. No. 7,505,775, which pursuant to 35 U.S.C. §119(a),claims the benefit of earlier filing date and right of priority toKorean Application No. 10-2004-0048431, filed on Jun. 25, 2004; KoreanApplication No. 10-2004-0053790, filed on Jul. 10, 2004; KoreanApplication No. 10-2004-0077649, filed on Sep. 25, 2004; and KoreanApplication No. 10-2005-0019211, filed on Mar. 8, 2005, the contents ofwhich are hereby incorporated by reference herein in their entirety.

FIELD OF THE INVENTION

The present invention relates generally to a wireless access system and,more particularly, to verifying availability of an idle-mode mobilesubscriber station in a wireless access system.

BACKGROUND OF THE INVENTION

Broadband wireless access systems typically support an idle-mode tominimize the power consumption of a mobile subscriber station (MSS).During the idle-mode, the MSS does not perform a handover procedure whenmoving between base stations in the same paging zone. Therefore, the MSSdoes not need to transmit uplink information for the handover procedure,which reduces corresponding power consumption.

A paging zone is defined as a zone that is controlled by a plurality ofbase stations called a paging group. Each of the base stations in thepaging group has the same paging cycle (Paging_Cycle) and the samepaging offset (Paging_Offset).

The MSS may make a request to a base station to switch to the idle-mode.The base station then provides a paging message including itspaging-group ID, a corresponding paging cycle, and a correspondingpaging offset. The corresponding MSS may thus be switched to theidle-mode. During the idle-mode, the MSS may determine whether tocontinue or terminate the idle-mode based on the paging message providedby the base station at each paging cycle.

If traffic needs to be transmitted by the MSS while in the idle-mode,the MSS may terminate the idle-mode. For example, the MSS may be enabledto terminate the idle-mode by the BS. Furthermore, if the MSS moves toanother paging zone or loses its sync while in an idle-mode and isunable to receive a paging at a predefined time, the MSS may terminatethe idle-mode.

When the MSS is in the idle-mode, the MSS normally receives a periodicpaging to secure its free move in the same paging zone withoutperforming the handover procedure as long as there exists no traffic toreceive or transmit.

A procedure of an MSS entering an idle-mode is explained in detail asfollows. The MSS delivers an idle-mode request message to a serving BSto enter the idle-mode. The serving BS provides a paging group ID, apaging cycle, a paging offset to the MSS via an idle-mode responsemessage. The serving BS also releases connection information to the MSS,as well as radio resources allocated to the MSS. Furthermore, theserving BS provides a MAC address of the MSS entering the idle-mode toBSs of its paging group so that each of the BSs may page thecorresponding MSS by the same paging cycle.

The MSS is allowed to enter the idle-mode via the idle-mode responsemessage after a determination of whether there is downlink traffic thatneeds to be delivered to the MSS by evaluating a paging message of abroadcast format delivered from the BS according to the paging cycle.Determinations are also made of whether to perform a ranging and whetherto maintain the idle-mode.

FIG. 1 is a diagram showing a format of a paging message received by anidle-mode mobile subscriber station (MSS) from a base station (BS).

Referring to FIG. 1, if the paging message states that there is downlinktraffic for the MSS, the MSS terminates the idle-mode and re-registersat a network to receive the downlink traffic. If the MSS is requested toperform ranging via the paging message, the MSS performs the ranging toallow the BS to update a location of the MSS and an idle-mode MSS list.If the paging message instructs the MSS to take no action, the MSSmaintains the idle-mode.

Thereafter, if uplink or downlink traffic needs to be communicated or ifthe paging group is handed over to another BS to terminate the MSSidle-mode, the BS informs the other BSs belonging to the same paginggroup so that the other BSs may remove the corresponding MSS from theidle-mode MSS list.

When the MSS is in the idle-mode, the MSS normally does not have uplinktraffic. Thus, in order to provide continuous availability of the MSS,the BS delivers the paging message to the MSS to enable thecorresponding MSS to perform the ranging. The BS may verify theavailability of the MSS only after receiving uplink information via aranging request from the MSS.

However, when the MSS is powered off, or when the MSS lies in a poorchannel environment, the MSS may fail to receive the paging message evenif the BS sets up the paging message (e.g., an action code is set to‘0x01 (perform ranging)’ or ‘0x02 (enter network)’) for delivery. Also,in such case, the BS may not receive the ranging request message fromthe MSS. Thus, if the MSS is unable to normally operate, the BS maydetermine that the MSS is no longer available. Furthermore, the BS mayneed to release all management resources (e.g., MAC address for paging,etc.) for the corresponding MSS and have other BSs of the same paginggroup remove the corresponding MSS from their idle-mode MSS lists.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to verifying availabilityof an idle-mode mobile subscriber station in a wireless access systemthat substantially obviates one or more problems of the related art.

An object of the present invention is to provide a method of updating alist of available idle-mode mobile subscriber stations (MSSs) by a basestation (BS) using a paging message delivered to MSSs.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, inone embodiment, a method of verifying availability of a mobilesubscriber station that is in an idle-mode includes requesting to a basestation by the mobile subscriber station to enter an idle-mode, whereinthe base station is associated with a paging group comprising aplurality of base stations, and receiving from the base station anidle-mode response command to enter the idle-mode, the idle-moderesponse command comprising at least one of the paging identifier, apaging cycle and a paging cycle offset. The method also includesreceiving from the base station a paging command comprising an actioncode associated with performing ranging while the mobile subscriberstation is in the idle-mode to verify availability of the mobilesubscriber station with respect to the base station, wherein if theranging is not successfully performed with the base station during apredetermined period, the base station continues to transmit the pagingcommand until a paging retrial count reaches a predetermined threshold.

The paging command may preferably be received when there is no downlinkdata. When the paging retrial count reaches the predetermined threshold,then the mobile subscriber station may preferably be removed from anidle-mode list maintained by the base station. The removal of the mobilesubscriber station of the idle-mode list may preferably be performed ineach one of the plurality of base stations in the paging group.

The predetermined period may preferably be the paging cycle.Alternatively, the predetermined period may be based on a timeexpiration associated with a maximum allotted time for the mobilesubscriber station to send a ranging request in response to the pagingcommand from the base station.

When the paging retrial count reaches the predetermined threshold, thenthe mobile subscriber station may preferably be removed from anidle-mode list maintained by a paging controller. The paging command maypreferably be received when there is traffic data to be downlinked tothe mobile subscriber station.

In another embodiment, a method of verifying availability of a mobilesubscriber station that is in an idle-mode includes requesting to apaging controller by the mobile subscriber station to enter anidle-mode, wherein the paging controller is associated with a paginggroup comprising a plurality of base stations, and receiving from thepaging controller an idle-mode response command to enter the idle-mode,the idle-mode response command comprising at least one of the pagingidentifier, a paging cycle and a paging cycle offset. The method alsoincludes receiving from the paging controller a paging commandcomprising an action code associated with performing ranging while themobile subscriber station is in the idle-mode to verify availability ofthe mobile subscriber station with respect to the paging controller,wherein if the ranging is not successfully performed with the pagingcontroller during a predetermined period, the paging controllercontinues to transmit the paging command until a paging retrial countreaches a predetermined threshold.

In yet another embodiment, a method of verifying availability of amobile subscriber station that is in an idle-mode includes receivingfrom the mobile subscriber station a request to enter an idle-mode,wherein a base station is associated with a paging group operativelyconnected to a plurality of base stations, and transmitting to themobile subscriber station an idle-mode response command to enter theidle-mode in response to the request to enter the idle-mode, theidle-mode response command comprising at least one of the pagingidentifier, a paging cycle and a paging cycle offset. The method alsoincludes transmitting to the mobile subscriber station a paging commandcomprising an action code associated with performing ranging while themobile subscriber station is in the idle-mode to verify availability ofthe mobile subscriber station with respect to the base station, whereinif the ranging is not successfully performed with the base stationduring a predetermined period, the base station continues to transmitthe paging command until a paging retrial count reaches a predeterminedthreshold.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings. It is to be understood that both the foregoinggeneral description and the following detailed description of thepresent invention are exemplary and explanatory and are intended toprovide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

FIG. 1 is a diagram showing a format of a paging message received by anidle-mode mobile subscriber station (MSS) from a base station (BS).

FIG. 2 is a diagram showing verifying of availability of an MSS based ona paging cycle in a wireless access system, according to one embodimentof the present invention.

FIG. 3 is a diagram showing verifying of availability of an MSS using atimer in a wireless access system, according to one embodiment of thepresent invention.

FIG. 4 illustrates a signaling operation of the MSS in idle-mode,according to one embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

In one embodiment, the present invention is implemented in a broadbandwireless access system. In another embodiment, the present invention isimplemented in a wireless communication system operating according to anon-broadband standard.

In yet another embodiment, when a mobile subscriber station (MSS) is inidle-mode, it checks for a perform ranging command from a serving basestation (serving BS) at every paging cycle. In other words, the servingBS periodically send a perform ranging command to the MSS to checkwhether the MSS is “alive”. If a perform ranging command is present,then the MSS may send a ranging request to the serving BS. If theserving BS does not receive a ranging request from the MSS, then theserving BS may repeatedly sends the perform ranging command until apaging retrial threshold is met. Once the paging retrial threshold ismet, the serving BS removes the MSS from the idle-mode MSS list.

In still another embodiment, a MSS enters an idle-mode and a serving BSis enabled to verify availability of the MSS using various parameters,including a Paging Retrial Count, and an Uplink Information ReceptionStandby Time (Ranging Request Message Reception Standby Time). A mobilesubscriber station is referred to as a MSS, regardless of whether or notit is in the idle-mode.

The availability of the MSS may be verified using the Paging RetrialCount, and the Uplink Information Reception Standby Time. Alternatively,the availability of the MSS may be verified using the Paging RetrialCount only. Alternatively, the availability of the MSS may be verifiedusing the Uplink Information Reception Standby Time only. The UplinkInformation Reception Standby Time may preferably be set equal to apaging cycle. Alternatively, the Uplink Information Reception StandbyTime may preferably be determined by a timer.

The MSS may lose synchronization of the paging messages periodicallydelivered from the serving BS, causing the MSS to fail to receive thepaging messages from the serving BS. If the MSS fails to receive thepaging messages from the serving BS, the MSS may perform are-registration procedure to the network. On the other hand, if theserving BS fails to receive uplink information from the MSS, despiterequiring the MSS to send the uplink information via the paging message,the serving BS may preferably decide that the MSS is unavailable.

The paging message is set up to deliver a ranging request to the servingBS from the MSS. The MSS may deliver the ranging request to the servingBS via a competition-based uplink ranging channel. If the serving BSrequests a ranging execution from the MSS, but fails to receive theranging request message from the MSS for a specified duration of aRanging Request Message Reception Standby Time, the serving BS maypreferably determine that the ranging has failed.

FIG. 2 is a diagram showing verifying of availability of an MSS based ona paging cycle in a wireless access system, according to one embodimentof the present invention.

Referring to FIG. 2, the MSS 210 enters the idle-mode by delivering aregistration release request (DREG-REQ) message to the serving BS 220.The serving BS 220 responds to the DREG-REQ message by delivering apaging group ID (PG-ID), a paging cycle (PG-CYC), and a paging offset(PG-OFFSET) to the MSS 210. The serving BS 220 also may releaseconnection information to the MSS 210, and radio resources allocated tothe MSS 210.

The serving BS 220 then provides a MAC address of the MSS 210 enteringthe idle-mode to BSs of the serving BS 220 paging group to enable eachof the BSs to page the MSS 210 by the same paging cycle. For example,each of the BSs may preferably transmit a paging message (MOB-PAG-ADV)to instruct the MSS 210 to request a ranging.

The MSS 210 may be allowed to enter the idle-mode via the registrationrelease command (DREG-PAG-ADV), and may determine whether downlinktraffic has been delivered to the MSS 210 via the broadcast-formattedpaging message delivered from the serving BS 220 according to the pagingcycle. The MSS 210 also may determine whether to execute the rangingand/or whether to maintain the idle-mode. In verifying the availabilityof the MSS 210 in FIG. 2, the paging cycle and the paging retrial countmay be utilized.

After transmitting the paging message (MOB-PAG-ADV) (Action Code=performranging or network entry) to the MSS 210, the serving BS 220 stands byfor the paging cycle until a ranging request message is received fromthe MSS 210. If the serving BS 220 does not receive uplink informationfrom the MSS 210 before the time for delivering the next paging message,e.g. after expiration of the paging cycle, the serving BS 220 maypreferably determine that the ranging has failed (ranging failure). Insuch case, the availability of the MSS 210 may be verified using UplinkInformation Reception Standby Time. The serving BS 220 may determinethat the MSS 210 is not available and remove the MSS 210 from anidle-mode MSS list. Alternatively, a paging controller that is connectedto a plurality of BSs may determine that the MSS 210 is not availableand remove the MSS 210 from an idle-mode MSS list.

The paging retrial count indicates a count of retrials made by theserving BS 220 failing in receiving the ranging request from the MSS210. The serving BS 220 may deliver the paging message ((MOB-PAG-ADV)(Action Code=perform ranging or network entry)) including a predefinedpaging retrial count to the MSS 210. If the serving BS 220 fails toreceive the ranging request from the MSS 210 despite delivery of thepaging message, the serving BS 220 may preferably determine that the MSS210 is not available and remove the MSS 210 from an idle-mode MSS list.Thus, the availability of the MSS 210 may be verified using twoparameters, paging cycle and paging retrial count.

If the serving BS 220 receives the ranging request from the MSS 210, theserving BS 220 (or paging controller) may update the availability of theMSS 210 via the idle-mode MSS list and notify the BSs belonging to thesame paging group to enable the BSs belonging to the same paging groupto update their idle-mode lists, via a backbone message.

On the other hand, if the serving BS 220 fails to receive the rangingrequest from the MSS 210 within a predetermined time via a setup of thepaging cycle and paging retrial, the serving BS may preferably removethe MSS 210 from an available idle-mode MSS list and release managementresources and information associated with the MSS 210. The serving BS220 may also preferably use a backbone message to notify the BSsbelonging to the same paging group to remove the MSS 210 from theiridle-mode MSS lists.

FIG. 3 is a diagram showing verifying of availability of an MSS using atimer in a wireless access system, according to one embodiment of thepresent invention.

Referring to FIG. 3, the availability of the MSS 210 may be verifiedusing a timer and a paging retrial count.

After transmitting the paging message (MOB-PAG-ADV) (Action Code=performranging or network entry), the serving BS 220 may stand by for anoperational time of the timer until a ranging request message isreceived from the MSS 210. If the serving BS 220 does not receive uplinkinformation from the MSS 210 before the time for delivering the nextpaging message (based on expiration of the timer), the serving BS 220may preferably determine that the ranging has failed. When verifying theavailability of the MSS 210 through uplink information reception standbytime only, the serving BS 220 may preferably determine that the MSS 210is not available and remove the MSS 210 from an idle-mode MSS list.

The serving BS 220 may deliver the paging messages ((MOB-PAG-ADV)(Action Code=perform ranging or network entry)) including a predefinedpaging retrial count to the MSS 210. If the serving BS 220 fails toreceive the ranging request from the MSS 210 despite the delivery of thepaging messages, the BS may decide that the MSS 210 is not available andremove the MSS 210 from an idle-mode MSS list.

The availability of the MSS 210 may be verified via two parameters,paging cycle and paging retrial count. The availability of the MSS 210may be determined according to a setup of each parameter.

In one embodiment, if an operational cycle of the timer is lower thanthe paging cycle, the serving BS 220 may determine the availability ofthe MSS 210 via the paging retrial count. In updating the availabilityof the MSS 210 via the paging retrial count, it may be unnecessary touse the timer. For example, if the serving BS 220 fails to receive theuplink information from the MSS 210 before a next paging time begins(after the delivery of the paging message (MOB-PAG-ADV)), the serving BS220 may determine that a ranging failure has occurred and perform apaging retrial. In another embodiment, when the paging retrial count isset to zero, if the timer expires after the paging message is deliveredto make the MSS 210 request an initial ranging, the serving BS 220 maydetermine that the MSS 210 is not available.

In yet another embodiment, a ranging request of the MSS 210 is performedvia a competition-based ranging channel. That is, the paging command maynot be based on the paging cycle. Instead, the retry of perform rangingis based on expiration of the timer. The timer expiration may be basedon the maximum allotted time for the MSS 210 to send a ranging request.In this embodiment, a similar procedure to that of the initial rangingmay be used. The MSS 210 may preferably stand by for a maximum 200 mswaiting for a ranging response message after the delivery of the rangingrequest message to the serving BS 220. After receiving the rangingresponse message from the serving BS 220, the MSS 210 may stand by for amaximum of two seconds to deliver the next ranging request message. Thestandby time of a maximum of two seconds may be applied tore-transmitting a next ranging request message due to failure to receivethe ranging response message. In still another embodiment, the rangingrequest retrial count of the MSS 210 is at least sixteen. Thus, byutilizing the two standby times and the ranging request retrial, theranging request standby time of the serving BS 220 may be determinedaccording to the timer. In yet another embodiment, the correspondingstandby time is at least thirty-three seconds.

In still another embodiment, when the serving BS 220 has previouslyassigned an uplink channel for the ranging to the MSS 210 via the pagingmessage (MOB-PAG-ADV), it is unnecessary that all BSs belonging to thepaging group assign the uplink ranging channel to the MSS 210 for anextended duration. Thus, in this embodiment, the availabilityverification of the MSS 210 via the timer may be mandatory. In the caseof mandatory availability verification, the timer may be set up by aframe unit. If there is no ranging request from the MSS 210 within theset frame unit, the serving BS 220 may release the uplink channelassigned to the MSS 210 and remove the MSS 210 from the idle-mode MSSlist.

In one embodiment, if the serving BS 220 receives the ranging requestfrom the MSS 210, the serving BS 220 may update the availability of theMSS 210 via the idle-mode MSS list and send a backbone message to enableother BSs belonging to the same paging group to update their idle-modeMSS lists.

In another embodiment, if the serving BS 220 fails to receive theranging request from the MSS 210 within the time predefined via thetimer and the paging retrial setup, the serving BS 220 may remove theMSS 210 from the idle-mode MSS list and release management resources andinformation associated with the MSS 210. The serving BS 220 may also usethe backbone message to notify the BSs belonging to the same paginggroup to remove the MSS 210 from their idle-mode MSS lists.

In one embodiment, a method of verifying availability of a mobilesubscriber station that is in an idle-mode includes requesting to a basestation by the mobile subscriber station to enter an idle-mode, whereinthe base station is associated with a paging group comprising aplurality of base stations, and receiving from the base station anidle-mode response command to enter the idle-mode, the idle-moderesponse command comprising at least one of the paging identifier, apaging cycle and a paging cycle offset. The method also includesreceiving from the base station a paging command comprising an actioncode associated with performing ranging while the mobile subscriberstation is in the idle-mode to verify availability of the mobilesubscriber station with respect to the base station, wherein if theranging is not successfully performed with the base station during apredetermined period, the base station continues to transmit the pagingcommand until a paging retrial count reaches a predetermined threshold.

The paging command may preferably be received when there is no downlinkdata. When the paging retrial count reaches the predetermined threshold,then the mobile subscriber station may preferably be removed from anidle-mode list maintained by the base station. The removal of the mobilesubscriber station of the idle-mode list may preferably be performed ineach one of the plurality of base stations in the paging group.

The predetermined period may preferably be the paging cycle.Alternatively, the predetermined period may be based on a timeexpiration associated with a maximum allotted time for the mobilesubscriber station to send a ranging request in response to the pagingcommand from the base station.

When the paging retrial count reaches the predetermined threshold, thenthe mobile subscriber station may preferably be removed from anidle-mode list maintained by a paging controller. The paging command maypreferably be received when there is traffic data to be downlinked tothe mobile subscriber station.

In another embodiment, a method of verifying availability of a mobilesubscriber station that is in an idle-mode includes requesting to apaging controller by the mobile subscriber station to enter anidle-mode, wherein the paging controller is associated with a paginggroup comprising a plurality of base stations, and receiving from thepaging controller an idle-mode response command to enter the idle-mode,the idle-mode response command comprising at least one of the pagingidentifier, a paging cycle and a paging cycle offset. The method alsoincludes receiving from the paging controller a paging commandcomprising an action code associated with performing ranging while themobile subscriber station is in the idle-mode to verify availability ofthe mobile subscriber station with respect to the paging controller,wherein if the ranging is not successfully performed with the pagingcontroller during a predetermined period, the paging controllercontinues to transmit the paging command until a paging retrial countreaches a predetermined threshold.

In yet another embodiment, a method of verifying availability of amobile subscriber station that is in an idle-mode includes receivingfrom the mobile subscriber station a request to enter an idle-mode,wherein a base station is associated with a paging group operativelyconnected to a plurality of base stations, and transmitting to themobile subscriber station an idle-mode response command to enter theidle-mode in response to the request to enter the idle-mode, theidle-mode response command comprising at least one of the pagingidentifier, a paging cycle and a paging cycle offset. The method alsoincludes transmitting to the mobile subscriber station a paging commandcomprising an action code associated with performing ranging while themobile subscriber station is in the idle-mode to verify availability ofthe mobile subscriber station with respect to the base station, whereinif the ranging is not successfully performed with the base stationduring a predetermined period, the base station continues to transmitthe paging command until a paging retrial count reaches a predeterminedthreshold.

Accordingly, the present invention enables a serving BS to check theavailability of an MSS. By checking the availability of the MSS, theserving BS prevents the MSS from failing to receive periodic pagingmessages, such as in cases where the power of the MSS is turned off orthe channel status is degraded.

The serving BS may deliver the availability update informationpertaining to the MSS to other BSs belonging to the same paging groupvia the backbone message, thereby preventing the BSs belonging to thesame paging group from delivering the paging message to an unavailableMSS.

Furthermore, when the uplink ranging channel is reserved or assigned tothe MSS, the serving BS may release the uplink channel assigned to theMSS and the management resources associated with the MSS. In so doing,power consumption of the MSS may be minimized and the idle-mode MSS listmay be efficiently updated.

In another embodiment of the present invention, the MSS may choose topower down (or turn off power) during idle-mode. By notifying the basestation of its decision to power down, the corresponding informationpertaining to the MSS retained by the network (the last base stationwhich granted the MSS to enter into idle-mode or the paging controller)can be erased.

In the embodiment of the present application, a ranging request messageand a ranging response message is used to accomplish powering off by theMSS. In operation, if the MSS attempts to power down while in the idlemode, a request to power down is transmitted via the ranging requestmessage to the network (the last base station, which granted the MSS toenter into idle-mode, or the paging controller). Subsequently, thenetwork receiving the power down request via the ranging request messagetransmits various information to the MSS via the ranging responsemessage.

FIG. 4 illustrates a signaling operation of the MSS in idle-mode isdescribed according to an embodiment of the present invention. Referringto FIG. 4, the MSS transmits to a first network entity a request messageto request to enter idle-mode via a de-registration request (DREG-REQ)message (S10). The first network entity can be a base station or apaging controller. Included in the request message is a MSS preferredsession information which the MSS prefers that the first network entityretain for expedited future re-entry to a network. This MSS preferredsession information includes information such as verificationinformation, internet protocol (IP) address information, the MSScapability, management connection identification, and informationessential to maintaining network service.

After receiving the request message, the first network entity broadcastsvia backbone channel(s) a notification to at least one or all othernetwork entities having the same paging identifications in the paginggroup so that the corresponding MSS can be added to each network entityof the paging group (S20).

In response to the request message, the first network entity transmits aselected session information to the corresponding MSS via ade-registration response command (DREG-CMD) (S30). The selected sessioninformation includes certain MSS service and operational informationuseful for expediting a future MSS network re-entry from idle-mode. Theselected session information can be same, different, or combinationthereof as the preferred session information requested by the MSS.Moreover, in the transmission of the DREQ-CMD, other information such aspaging cycle, paging offset, and paging identification can be included.The DREG-CMD is a command or a message granting the MSS to enteridle-mode as requested.

Upon receipt of the DREG-CMD from a second network entity, the MSSenters idle-mode. During idle-mode, the MSS can receive a pagingmessage(s) at specified time slots or intervals from the first networkentity (S40). The paging message includes various information such aswhether there is any downlink traffic or when to terminate idle-mode.

If the MSS moves to the second network entity within the same paginggroup which has the same paging identification (S50), the MSS mayreceive paging message(s) from the second network entity at same pagingcycle and paging offset as received from the first network entity (S60).

During this period (idle-mode), the MSS can experience power depletionor simply choose to power down. The corresponding MSS transmits to thesecond network entity a message indicating power off/down (e.g., powerdown indicator) via a ranging request message (S70). The second networkentity then notifies the first network entity that the MSS has powereddown and requests the first network entity to de-register or delete theMSS information from the list of MSS in idle-mode (S80). In addition,the second network entity can transmit to a network entity which retainsinformation on the MSS via a message indicating the idle-mode status ofthe MSS, for example.

At the same time, the MSS may attempt to complete a location update onceas part of its orderly power down procedure. This mechanism enables thesecond network entity to update the exact status of the MSS and todelete all information for the MSS. Moreover, this mechanism enables thesecond network entity to discontinue idle-mode paging control for theMSS at the time of power down.

After the second network entity notifies the corresponding MSS that thepower down location update has been successfully executed, the secondnetwork entity may release all idle-mode retaining information relatedto the MSS (S90). It is possible for the second network entity to failto update power down information. In such case, the second networkentity (e.g., paging controller) may perform availability check usinglocation update polling. Unavailability of the MSS may be determined andthe second network entity shall delete all idle-mode retaininginformation if the MSS does not answer for the second network entity'slocation update polling up to ‘paging retry count’.

The application of the embodiment of the present invention is notlimited to requesting for power down in a coverage area of a differentbase station. Rather, it is possible to power down in the in the basestation which granted idle-mode without ever leaving its coverage areaor returning to its coverage area. The notification of powering down bythe MSS provides effective and efficient management of the resources inthe coverage are of the BS. Instead of BS determining the status of theMSS, by MSS notifying the BS of its intent to power down, the BS canefficiently manage the MSS and the resources associated with the BS.

It will be apparent to those skilled in the art that variousmodifications and variations may be made in the present inventionwithout departing from the spirit or scope of the inventions. Thus, itis intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. A communication system for controlling idle mode activity, thecommunication system comprising a mobile subscriber station, a pluralityof base stations belonging to a same paging group and a pagingcontroller, the communication system further comprising: the mobilesubscriber station for: transmitting a first request message to aserving base station in order to enter idle mode; receiving a responsemessage from the serving base station and entering idle mode, theresponse message including paging information that includes informationrelated to at least paging grouping identification, paging cycle, orpaging offset; receiving a paging message during a specified timeinterval from one of the plurality of base stations; and performing apower down location update by transmitting a ranging request messagecomprising a power down indicator to enable the paging controller toupdate the exact status of the mobile subscriber station, delete allinformation for the mobile subscriber station and discontinue idle modepaging control for the mobile subscriber station; and the pagingcontroller for: determining whether the power down location update issuccessful; releasing all idle mode retaining information related to themobile subscriber station if the power down location update issuccessful; performing a power availability check using location updatepolling if the power down location update is unsuccessful; and deletingall the idle mode retaining information if the mobile subscriber stationdoes not answer for the location update polling before a paging retrycount is reached.
 2. The communication system of claim 1, wherein therequest message includes preferred session information of the mobilesubscriber station to expedite future network re-entry to the network.3. The communication system of claim 2, wherein the preferred sessioninformation includes at least one of verification information, Internetprotocol address information, and information associated with networkservice.
 4. The communication system of claim 1, wherein the responsemessage further includes service and operational information forexpediting a future network re-entry from idle mode.
 5. Thecommunication system of claim 1, wherein the paging message includesinformation that indicates whether to terminate idle mode.
 6. Thecommunication system of claim 1, wherein: each of the plurality of basestations belonging to the same paging group maintains an idle mode list;and each idle mode list in the same paging group is updated whenentering the idle mode in order to remove the mobile subscriber stationin response to a backbone message from at least one of the plurality ofbase stations, the backbone message associated with unavailability ofthe mobile subscriber station in the same paging group.